Alcohol dependence (AD), of all genetically influenced traits, is one of the most costly to society, in the United States and worldwide. Genetic epidemiologic studies consistently report the heritability of AD to be ~0.50-0.60. Genomewide linkage studies from different research groups have only rarely reported linkage peaks that attain conventional statistical significance, but several such peaks have been replicated independently in numerous studies, supporting their probable validity; and candidate genes based on linkage results have in several cases been replicated strongly and consistently across different research groups (including ours). Although AD cuts across society, minority populations, and specifically African-Americans (AAs), are understudied. To address this issue, we started a project in 2002 (AA11330) of which one goal was the collection of a sample of AA alcohol-dependent cases and controls (for mapping by admixture linkage disequilibrium, and other gene mapping methods). We have now recruited a total of 1500 unrelated AA subjects, all of whom were assessed with the state-of-the-art SSADDA (Semi-Structured Assessment for Drug Dependence and Alcoholism), which includes considerable detail regarding AD beyond merely the diagnostic criteria. We will augment our SSADDA-assessed control sample with additional subjects from the NIMH Genetics Initiative, yielding a sample of 1500 AD cases and 1500 controls. Based on a smaller sample (1000/1000), we previously proposed a genomewide association study through CIDR, using the Illumina HumanHap650Y marker set, which was approved for genotyping with the contingency that an additional independent NIH-supported project be funded. That approval has been extended to accommodate the present amended proposal. This would be a pioneering WGAS in an AA AD population; we expect to obtain invaluable new insights into AD in the AA population, and into the structure of the AA population; and will also address associated phenotypes, including comorbid disorders (such as cocaine or opioid dependence). We propose replication of most-significant signals in additional AA and EA samples; and collection of an additional 1250 SSADDA-assessed affected subjects to permit a more powerful GWAS in YR05. PUBLIC HEALTH RELEVANCE: Alcohol dependence is genetically influenced. The purpose of this project is to use a new and powerful technique, genomewide association analysis, to identify genes that influence risk for alcohol dependence in African-Americans, and to replicate key findings. Successful completion of this research would be expected to increase our understanding of alcohol dependence, and potentially to lead to early identification of susceptible individuals, and to new treatments.